Method and apparatus for making a tubular composite structure

ABSTRACT

A tool for making a composite tubular structure, such as the inner skin of an acoustic liner, includes a base on which are mounted a plurality of sectors, each having an outer panel provided with a predetermined shaped surface. The predetermined shaped surface corresponds to a portion of the contour of the tubular structure to be formed. At least one of the sectors is fixed relative to the base while the remaining sectors are movable in a radial direction and separable from all the other sectors. The sectors are provided with air bearings to facilitate movement along a radial direction. Splice plates are used to form a joint between the outer panels of adjacent sectors. After composite material is applied on the outer panels, a vacuum bag is formed to surround the composite material and also the joint areas on the inner surface of the tool. The entire tool may be placed in an autoclave for curing. The thus-formed composite tubular structure may be remounted on the tool for bonding to additional exterior layers.

CROSS REFERENCE TO RELATED APPLICATIONS

None.

BACKGROUND OF THE INVENTION

The present invention is related to a method and apparatus for makingtubular composite articles, such as an acoustic liner for an aircraftnacelle.

An acoustic inlet barrel for a nacelle inlet may comprise a number oflayers, including a perforated inner skin, an acoustic core, and animpervious outer skin. Typically, the inner skin is formed from sectorsthat are bolted together at axially extending seams. Ideally, however,the perforated skin has no internal seams or other features which maydegrade the acoustic performance of the barrel.

U.S. Published Patent Application No. 2004/0065775 discloses a tool formolding an air intake, and more specifically for forming a one-pieceinner skin having no internal seams. The tool comprises a mandrel havingfour arcuate sectors, a fixed sector that does not move during normaloperation to the tool, two movable articulated sectors each hingedlyconnected to either side of the first sector; and a movable key sectorwhich is independent from the other sectors and insertable between thearticulated sectors. By virtue of the hinges, the articulated sectorsremain connected to the fixed sector and cannot be separated therefrom.Locks are provided to secure the key sector to the articulated sectors.When in the molding position, the four sectors together define, by theirexternal surfaces, a continuous surface corresponding to the internalsurface of an air intake. A control device, disconnectable from themandrel, may be used to adjust the movable sectors between a moldingposition and an non-molding position.

SUMMARY OF THE INVENTION

In one aspect, the present invention is directed to a tool for making acomposite tubular structure, the tool being adjustable between a moldingposition and a non-molding position. Such a tool comprises a base; and aplurality of sectors mounted on the base, the plurality of sectorsincluding at least one fixed sector that is fixed relative to the baseand at least two movable sectors, each of the movable sectors beingmovable in a radial direction and separable from all the other sectors.

The tool may further comprise splice plates positioned between adjacentsectors, when the tool is in the molding position. The splice plates mayhave a T-shaped cross-section, and are configured to maintain alignmentof adjacent sectors. The outer surfaces of the splice plates may form aportion of an outer contour of the tool and maintain a maximum stepdifference along edges of adjacent sectors that is less than 0.05inches.

Each of the movable sectors may rest on at least one air bearing tofacilitate movement in said radial direction; the at least one airbearing may comprise a flat portion of a movable sector. The tool mayfurther comprise a nozzle attached to said movable sector andconnectable to a compressed air source to thereby supply air to said atleast one air bearing.

The tool may further comprise at least one removable hand wheeloperatively connected to a corresponding removable shaft, whereinturning the hand wheel moves a corresponding sector in the radialdirection. The at least one removable hand wheel and the removable shaftmay be mounted on separate hinged blocks. The sectors and the hingedblocks may be made from a same material so that they have a commoncoefficient of thermal expansion.

The tool may further comprise a pair of cutouts formed in the upperfacing corners of adjacent sectors, the cutouts merging to form a notch,when the tool is in the molding position.

The tool may have a total of four sectors, one fixed sector and threemovable sectors.

In another aspect, the present invention is directed to a method formolding a tubular composite inner skin for an acoustic inner barrel. Theinventive method comprises providing a tool that is adjustable between amolding position and a non-molding position, the tool comprising a baseand a plurality of sectors mounted on the base, the plurality of sectorsincluding at least one fixed sector that is fixed relative to the baseand at least two movable sectors, each of the movable sectors beingmovable in a radial direction and separable from all the other sectors;adjusting the movable sectors until the tool is in the molding position;applying composite material on an outer surface of each sector; curingthe composite material to form an inner skin; and removing the innerskin from the outer surface.

In still another aspect, the present invention is directed to a tool formaking a composite tubular structure, the tool being adjustable betweena molding position and a non-molding position. The tool comprises abase, a plurality of sectors mounted on the base, the plurality ofsectors including at least one fixed sector that is fixed relative tothe base and at least two movable sectors. Each of the movable sectorsis movable in a radial direction and separable from all the othersectors, each of the movable sectors rests on at least one air bearingto facilitate movement along an upper surface of said base, and each ofthe movable sectors is operatively connected to a removable hand wheeloperatively connected to a corresponding removable shaft, whereinturning the hand wheel moves a corresponding sector. The tool alsoincludes a plurality of splice plates, with one splice plate positionedbetween adjacent sectors, when the tool is in the molding position.

In still another aspect, the present invention is directed to a tool formaking a composite tubular structure, the tool being adjustable betweena molding position and a non-molding position. The tool comprises abase, a plurality of sectors mounted on the base, the plurality ofsectors including at least one fixed sector that is fixed relative tothe base and at least two movable sectors; and a plurality of spliceplates, with one splice plate positioned between adjacent sectors, whenthe tool is in the molding position.

The splice plates may have a T-shaped cross-section, and are configuredto maintain alignment of adjacent sectors. The outer surfaces of thesplice plates may form a portion of an outer contour of the tool andmaintain a maximum step difference along edges of adjacent sectors thatis less than 0.05 inches.

In yet another aspect, the present invention is directed to a tool formaking a composite tubular structure, the tool being adjustable betweena molding position and a non-molding position. The tool comprises abase, and a plurality of sectors mounted on the base, the plurality ofsectors including at least one fixed sector that is fixed relative tothe base and at least two movable sectors; wherein each of the movablesectors rests on an air bearing to facilitate movement along an uppersurface of said base.

In yet another aspect, the present invention is directed to a tool formaking a composite tubular structure, the tool being adjustable betweena molding position and a non-molding position. The tool comprises abase, and a plurality of sectors mounted on the base, the plurality ofsectors including at least one fixed sector that is fixed relative tothe base and at least two movable sectors, wherein each movable sectoris operatively connected to a removable hand wheel operatively connectedto a corresponding removable shaft, wherein turning the hand wheel movesa corresponding sector.

In yet another aspect, the present invention is directed to method formolding a tubular composite inner skin for an acoustic inner barrel. Theinventive method comprises providing a tool that is adjustable between amolding position and a non-molding position, the tool comprising a baseand a plurality of sectors mounted on the base, the plurality of sectorsincluding at least one fixed sector that is fixed relative to the baseand at least two movable sectors, all of the movable sectors beingmovable in a radial direction relative to a center of the base; placinga tubular composite inner skin over the tool; positioning an acousticcore over the inner skin and bonding the acoustic core thereto;positioning an outer skin over the acoustic core and bonding the outerskin thereto; and removing the bonded inner skin/core/outer skincomposite structure from the tool.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a tool in accordance with the presentinvention in the molding state.

FIG. 2 is a side view of the tool of FIG. 1.

FIG. 3 is a top view of the tool of FIG. 1.

FIG. 4 is a perspective view of the tool of FIG. 1 in a collapsed statewith the movable sectors brought radially inward, such as when a partformed on the tool is to be removed.

FIG. 5 is a perspective view of the base of the tool of FIG. 1.

FIG. 6 shows a detailed view of the structural support and positioningassembly of a movable sector from outside the tool.

FIG. 7 shows a detailed view of the structural support and positioningassembly of a movable sector from inside the tool.

FIG. 8 shows a partially exploded view of a tool in accordance withclaim 1, with the splice plate seen in isolation;

FIG. 9 shows a close up of a splice plate positioned between a pair ofadjacent sectors and FIG. 9 a shows a detailed view of a portion of FIG.9.

FIG. 10 shows sealant beads on the outer surface of the tool.

FIG. 11 shows a sealant bead on the inner surface of the tool around asplice plate.

FIG. 12 shows the principal steps in an exemplary process for making atubular composite using the tool of FIG. 1.

FIG. 13 shows the principal steps for using the tool of FIG. 1 toassemble an acoustic inner barrel.

DETAILED DESCRIPTION OF THE INVENTION

The contents of aforementioned U.S. published Patent Application No.2004/0065775 are incorporated by reference to the extent necessary tounderstand the present invention.

FIGS. 1-3 show perspective, side and top views, respectively, of a tool100 in accordance with the present invention. As seen in FIGS. 1-3, thetool is in the “molding” state—i.e., the tool 100 is ready to have oneor more layers of composite material applied to its axially extendingtubular exterior surface to form a tubular composite member, such as aninner skin of an acoustic inner barrel for an aircraft gas turbineengine. This contrasts with a “collapsed” state, such as seen in FIG. 4,in which a tubular composite member formed on the tool may be removedfrom the tool.

The tool 100 comprises a plurality of components. Preferably, all thecomponents of the tool are formed of a material having a coefficient ofthermal expansion that is similar to that of graphite-epoxy composite, amaterial commonly used to form a tubular composite. By selecting a toolmaterial having a coefficient of thermal expansion that is similar tothat of graphite-epoxy, one can help mitigate separation effects betweenthe tool and the composite being formed thereon, during heating andcooling. In a preferred embodiment, the tool components are made ofInvar “36”®.

The tool 100 includes a removable top ring 170, a plurality of sectors182, 184, 186, 188, and a base 190. Sector 182 is a fixed sector whilesectors 184, 186 and 188 are movable sectors. In one embodiment the basehas a diameter of about 134″ and height of about 123″. The tool alsocomprises additional features to help position the movable sectors andadjust each of the movable sectors between a molding position and anon-molding position, as discussed below. During normal use, a movablesector is considered to occupy a ‘molding position’ when it is at itsradially outermost position; and is considered to occupy a ‘retractedposition’ whenever it is moved in a radially inward direction relativeto its ‘molding position’.

In the present application, we refer to the entire tool as being in a‘molding position’ when all of the movable sectors are in moldingpositions; we refer to the entire tool as being in a “collapsedposition” when any one of the movable sectors is retracted; and we referto the tool as being in an “non-molding position” when all of movablesectors have been retracted.

The removable top ring 170 helps ensure the position of the varioussectors at their top end when the tool is in the molding position. Inthe embodiment shown, the top ends of the sectors correspond to theforward (or upstream) end of the tubular inner skin formed using thetool.

As best seen in FIG. 5, the base 190 is circular in shape and comprisesan upper surface 192 and a skirt 194 extending downwardly therefrom. Aset of four wheels 196 is attached to the bottom 193 of the base 190 tohelp roll the base along a floor or other surface on which the base 190rests. The bottom 193 of the base 190 is also provided with at least onepair of tubular members 198 traversing the base in a chord-like manner.The tubular members 198 are configured and dimensioned to serve asforklift receiving structures suitable for receiving forklift prongs, tofacilitate lifting and transporting the base 190. The base upper surface192 has an annular shape and is provided with a plurality of accessopenings 368, discussed further below.

In one embodiment, the tool 100 comprises four sectors. However, it isunderstood that in other embodiments, the tool may comprise othernumbers of sectors.

Each sector comprises an outer panel, shown generally as 180, providedwith a shaped surface 183 that conforms to a portion of the compositetubular structure to be formed using the tool. In the embodiment shown,sector 182, which preferably subtends about 120° relative to a centralaxis A of the base 190, is a fixed sector and so does not move relativeto the base upper surface 192, when the tool is adjusted between amolding position and a collapsed position. The remaining three movablesectors 184, 186 and 188, however, do move relative to the base uppersurface 192. In one embodiment, each of these movable sectors isarranged to move in a radial direction, relative to the central axis Aof the base 190; each of the movable sectors being completely separablefrom the other sectors.

While the base 190 preferably is circular, it may have some other shapeinstead. In such case, it is understood that the movable sectors can bemoved relative to some axis around which they are centered.

As best seen in FIG. 4, movable large sector 184 is diametricallyopposite to fixed sector 182 and also subtends about 120° relative tothe axis A. Movable smaller sectors 186 and 188 are positioned betweensectors 182 and 184 and are diametrically opposite one another. Each ofthe smaller movable sectors subtends about 60° relative to the axis A.

FIGS. 6 and 7 show how movable sector 188 is supported on the base uppersurface 192, and moves in a radial direction along the base uppersurface 192. It is understood that movable sectors 184 and 186 also havecomparable features and behave in a similar manner.

The movable sector 188 comprises an outer panel 189 that is supported bya pair of support columns 310 which themselves project upwardly from asector support plate 302. The weight and weight distribution of thesector 188 is such that its center of gravity is over the sector supportplate 302. Mounted on the sector support plate 302 is a radially outwardshaft mount 348, discussed further below.

The sector support plate 302 rests upon a pair of spaced apart slidingabutment plates 304 a, 304 b. Bolts are used to secure the sectorsupport plate 302 to the sliding abutment plates 304 a, 304 b to ensurethat they do not move relative to one another.

Each sliding abutment plate 304 a, 304 b rests upon the base uppersurface 192. The bottom surface 305 of each sliding abutment plate 304a, 304 b, and at least portions of the base upper surface 192 that arein abutment with the bottom surface 305 of sliding abutment plates 304a, 304 b, are preferably machined, sanded or otherwise treated to formflat, smooth, and parallel surfaces and reduce friction therebetween.

The flat bottom surface 305 of each sliding abutment plate 304 a, 304 bis further provided with at least one opening (not shown) whichcommunicates with one or more or nozzles 306 connectable to a supply ofcompressed air. In general, a plurality of such nozzles 306 areprovided. In one embodiment, for movable sector 188, a total of foursuch nozzles are provided. A larger movable sector may have six, or evenmore, such nozzles.

The at least one opening may comprise a simple circular hole, preferablyhaving a diameter on the order of 0.5 inches or so. When a pressurizedair source is connected to the nozzles 306, air is forced through theopening and pushes against the base upper surface 192, further reducingthe friction between the flat bottoms 305 of sliding abutment plates 304a, 304 b and the base upper surface 192. Under these conditions, thesliding abutment plates 304 a, 304 b serve as air bearings 304 a, 304 b,which facilitate translation of movable sector 188 in a radial directionalong the base upper surface 192.

The resulting air bearings 304 a, 304 b provide several benefits. First,they may obviate the need for lubricant on abutting surfaces that sliderelative to one another. Eliminating lubricant both simplifies use andhelps reduce contamination of the molded composite structure. Second,they permit each movable sector to be moved along the radial directionby just one person manually turning a hand wheel (discussed furtherbelow), even though the movable sectors may weigh upwards of 2,500pounds or more.

Once the movable sector 188 is moved in a radial direction to near adesired position, locating pins 358 are used to secure the movablesector 188 to the base upper surface 192. The locating pins 358 passthrough aligned openings (not shown) in the sector support plate 302 andthe sliding abutment plate 304, and into locating openings 368 formed inthe base upper surface 192. This helps ensure repeatable positioning ofthe movable sector 188 relative to the base upper surface 192.

The movable sectors 184, 186, 188 are translated along the radialdirection by means of manually operated hand wheels 224, 226, 228,respectively. Hand wheels 224, 226, 228 are operatively connected tothreaded shafts 234, 236, 238 so that turning a hand wheel turns thecorresponding shaft. While hand wheels are preferred, it is alsopossible to use small motors (not shown) mounted either on the base oron the movable sectors, to selectively move the movable sectors betweena molding position and a retracted position. Such motors may beelectric, pneumatic, or driven by other power.

As best seen in FIG. 5, mounted on the base upper surface 192 are aplurality of radially inward shaft mounts 214A, 216A, 218A and acorresponding plurality of hand wheel mounts 214B, 216B, 218B. Radiallydirected guide members 214C, 216C, 218C are positioned betweencorresponding radially inward shaft mounts 214A, 214B, 214C,respectively, and hand wheel mounts, 214B, 216B, 218B, respectively.

Each of the radially inward shaft mounts 214A, 216A, 218A comprises ablock into which the distal end of its corresponding shaft 234, 236,238, respectively, is inserted.

Mounted on each of the sector support plates is a radially outward shaftmount. As best seen in FIGS. 6 and 7, sector support plate 302, which isassociated with movable sector 188, is provided with radially outwardshaft mount 348. Thus, shaft 238 is supported at its distal end byradially inward shaft mount 218A and is supported at its proximal end byradially outward shaft mount 348. It is understood that shafts 234 and236 are supported in a comparable manner.

Radially outward shaft mount 348 comprises a hinged block of a firstkind, whose structure and operation are known to those skilled in theart. Such hinged blocks have a top portion hingedly connected to abottom portion, and a hand knob to tighten the two in the closedposition. When the hinged block is closed and the top portion overlaysthe bottom portion, an opening is formed between the two portions. Thisopening is threaded so as to accommodate the complementarily threadedshaft 238. When the threaded shaft 238 is turned, the shaft threadscause the radially outward shaft mount 348 (and thus the movable sector188 attached thereto) to travel along the shaft 238. It is understoodthat the radially outward shaft mounts mounted on the other two sectorsupport plates (e.g., radially outward shaft mount 344, seen in FIG. 4)also comprise such a hinged block, and shafts 234, 236 act in a similarmanner.

Each of the hand wheel mounts 214B, 216B, 218B comprises a hinged blockof a second kind, whose structure and operation are also known to thoseskilled in the art. The hand wheel mounts 214B, 216B, 218B are similarin construction to radially outward shaft mount 348, except that theopening formed between the top and bottom portions is not threaded. Foreach movable sector, the corresponding hand wheel mount, the radiallyinward shaft mount and the radially outward shaft mount are allcollinear.

Also, while hinged blocks are preferred, one may instead useconventional blocks which would be unbolted from the base or the movablesector, each time the hand wheel or shaft was to be removed. Other meansand mechanisms for moving the sector support plate 302 (and the movablesector mounted thereon) relative to the base upper surface are alsopossible, as will be recognized by those skilled in the art.

When the movable sectors are to be moved, each hand wheel is mated to acorresponding shaft with the former being retained in a correspondinghand wheel mount and the latter being retained near its proximal end ina corresponding radially outward shaft mount and near its distal end ina corresponding radially inward shaft mount.

When a given movable sector need no longer be moved, such as uponreaching its molding position, its two hinged blocks, i.e., the handwheel mount and the radially outward shaft mount, may be opened, and thehand wheel and the shaft removed. As discussed further below, the handwheel and the shaft are removed when the tool is placed in an autoclaveor other oven for curing. This allows easier access to portions of thetool, and also may help prevent contamination of the autoclave duringthe curing process by lubricants that may be present on such components.

When adjusting the tool 100 from a first position (such as seen in FIGS.1-3) in which composite material may be applied on an outer surface ofthe tool to a second position (such as seen in FIG. 4) in which theinner skin may be removed after the curing process, the two smallermovable sectors 186, 188 are retracted first, and then the largermovable sector is retracted. Retraction of the tool 100 into anon-molding position in this fashion allows the inner skin to be removedtherefrom. It is understood, however, that the distances by which thevarious movable sectors are retracted will depend on the shape and sizeof the tubular composite being formed.

FIGS. 8 and 9 show a splice plate 402, or “splitter bar”, in accordancewith the present invention. The splice plate 402 is positioned betweenthe facing edges 414, 416 of adjacent sectors 184, 186, respectively.The splice plate 402 connects adjacent sectors 184, 186 and maintainstheir mutually facing edges in alignment with one another And as seen inFIGS. 1-3, the outer surfaces of the splice plates form a portion of anouter contour of the tool, when the tool is in the molding position. Thesplice plates are constructed and arranged to provide the exterior ofthe tool 100 with a smooth outer surface. One way to characterize thesmoothness of the outer surface is with reference to the maximum stepdifference along the edges of adjacent sectors. In one embodiment, thisstep difference is less than 0.05 inches. More preferably, however, thestep difference is on the order of less than 0.002 inches.

As best seen in FIGS. 9 and 9 a, the splice plate 402 has a T-shapedcross section. The head 404 of the splice plate 402 faces the inside ofthe tool while the outwardly face base 406 of the radially extending leg408 of the splice plate 402 faces the outside of the tool and forms anarrow, vertically directed portion of the tool's exterior surface. Thecircumferentially directed sides of the leg 408 abut radially inwardlyextending flanges 434, 436 formed on the facing edges 414, 416,respectively. Bolts 440 pass through a first flange 434, through theradially extending leg 408 of the splice plate, and into the secondflange 436. This allows the adjacent sectors 184, 186 to be boltedtogether to provide a smooth outer surface on the tool and therebyminimize any steps that might otherwise form where adjacent sectorsmeet. INCONEL® Belleville (spring) washers are used in conjunction withthe bolts 440 to help retain torque during thermal cycling in anautoclave or other oven, during the curing process.

When the tool 100 is being adjusted into the molding position, thesplice plate 402 is added last, after the movable segments have beenpositioned. When the tool 100 is being adjusted from the moldingposition to the non-molding position for removal of a part formedthereon, the splice plates 402 are removed first. Removing the spliceplate first relieves tension between the tool and the formed part.

In the foregoing discussion of FIGS. 8 and 9, only a single spliceplate, between two specific adjacent sectors was discussed. It isunderstood, however, that such splice plates are positioned between eachadjacent pair of sectors, be the sectors fixed or movable.

As seen in FIGS. 1, 2 and 9, notches 450 appear between all pairs ofadjacent sectors (all four corners of all the sectors 182, 184, 186 and188 having been provided with cutouts 454, 456) both at the top end andat the bottom end of the splice plates 402. As discussed further below,these notches 450 are regions where ends of polymer films meet to sealthe composite material, prior to and during curing.

To form a composite inner skin for an aircraft nacelle, the tool 100 isadjusted to the molding position and composite material is applied in apre-determined horizontal band between the upper and lower edges 592,594 (see FIG. 10) of the tool sectors 182, 184, 186, 188 (and also overthe outwardly facing base 406 the splice plates 402). The compositematerial, and the techniques used to apply the composite material to thetool, are well known to those skilled in the art.

After the composite material has been applied, it is covered withplastic film and vacuum sealed. The plastic film is placed on theoutside of the tool over the composite material, and also on the insideof the tool over the splice plate regions. Beads of sealant are used toadhere the plastic film to the tool.

As seen in FIG. 10, the beads of sealant 602, 604 run circumferentiallyaround the outer surface of the tool 100. The bead 602 is applied to thetool outer surface, above the upper axial extent of the compositematerial. Likewise, the bead 604 is applied to the tool outer surfacebelow the lower axial extent of the composite material. In other words,and as a result, the composite material is entirely between the bead 602and bead 604. Upper outer bead 602 is proximate the upper edge 592 ofthe sectors and crosses the upper notches 450U. Similarly, lower outerbead 604 is proximate the lower edge 594 of the sectors and crosses thelower notches 450L. As seen in FIG. 11, a bead 606 is placed all aroundthe splice plate 402 on the inner surface of the tool. The bead 606encircles the splice plate 402 joining two adjacent sectors, and crossesboth the upper notch 450U and the lower notch 540L, but from the inside.As seen in FIGS. 10 and 11, at notch 450U, bead 602 overlaps bead 606while at notch 450L, bead 604 overlaps bead 606.

In FIG. 10, the bead 606 is shown as a dashed line, since it is actuallyon the inside of the tool, while in FIG. 11, beads 602 and 604 are shownas dashed lines since they are actually on the outside of the tool. Asis known to those skilled in the art, vacuum bag sealant tape (two-sided“chromate tape” with peel-off backing on both sides), such as model no.GS 213-3, available from General Sealants of Industry, CA may besuitable for use as beads 602, 604, 606.

With the upper outer bead 602, the lower outer bead 604 and the innerbead 606 in place, a first portion of polymer film, such as a nylonfilm, is placed on the outer surface of the tool 100. This first portionof film is a single piece that extends around the entire circumferenceof the tool and is overlapped in the circumferential direction by aninch or so, the overlapping ends secured by an axially extending pieceof chromate tape. This first portion of nylon film is of sufficientheight to contact the upper and lower beads 602, 604. Preferably, theupper edge of the nylon film extends above the upper bead 602 around theentire circumference of the tool, while the lower edge of the firstportion of nylon film extends below the lower bead 604 around the entirecircumference of the tool. The first portion of the film also extendsacross each notch 450U, 450L, and is secured to those portions of beads602 and 604 that extend across each notch as seen in FIGS. 10 and 11. Inone embodiment, an IPPLON® KM 1300 nylon film, available from AirtechInternational, Inc. of Huntington Beach, Calif. is used.

A second portion of nylon film, which is sized to cover at least theentire splice plate 402 and contact the entire inner bead 606 is thenapplied on the inside surface of the tool. It is understood that foursuch inner beads 606 and four such second portions of nylon film areused, each covering one of the four splice plates 402 in the embodimentshown. Each inner bead 606 extends across each notch 450U and 450L, andthereby secures each second film portion across each notch. At eachupper notch 450U, the upper bead 602 and the upper portion of the innerbead 606 overlap each other as they extend circumferentially across eachnotch. Similarly, at each lower notch 450L, the lower bead 604 and thelower portion of inner bead 606 overlap each other as they extendcircumferentially across each notch. As a result of the overlaps of theouter beads 602, 604 with upper and lower portions of the inner bead 606at the notches 450U, 450L, when the first and second portions of filmare applied to their respective bead on the tool, the first film portionand the second film portion sealingly join and engage each other. Inthis manner, a vacuum bag is formed, the vacuum bag creating a sealaround the splice plates 402 and the adjoining areas where the edges ofthe sectors 182, 184, 186, 188 are present.

An exemplary use of the tool 100 is presented next with reference toFIG. 12. This exemplary use illustrates one embodiment of a process 500for making a composite inner skin of a 360° acoustic inner barrel for anacelle inlet, using the tool 100. The process entails a number ofphases: tool surface preparation 502; tool assembly 504 application ofcomposite material 506; preparation for curing 508; curing in anautoclave 510; and composite inner skin removal 512.

First, the tool surface is prepared, in a known manner. The tool surfacepreparation process 502 entails:

-   -   (1) Adjusting the tool into a non-molding position (if not        already done);    -   (2) Cleaning the tool with a solvent; and

(3) Applying a release agent, such as FREEKOTE™ to the outer surfaces ofthe sectors.

Next, the tool is assembled and configured for use. As seen in FIG. 12,the tool assembly process 504 entails:

-   -   (1) Moving the movable tool sectors 184, 186, 188 in a radially        outward direction into their molding position. Pressurized air        is used to form air bearings, as described above, to facilitate        movement of the sectors;    -   (2) Installing the splice plates 402 between adjacent sectors by        bolting each plate to its respective pair of opposing flanges on        the sectors;    -   (3) Installing pins to secure the sectors.    -   (4) Positioning the top ring 170, such as by lowering it onto        the sectors by means of a crane and then bolting it to upper        portions of the sectors; and    -   (5) Opening the hinged blocks 214B, 216B, 218B, 348 and removing        the hand wheels 224, 226, 228 and shafts 238.

After the tool 100 is assembled, composite material is applied to theexternal surface of the tool in a conventional lay-up process andcompacted by vacuum. The composite material application and compactionprocess 506 entails:

-   -   (1) Laying on plies of composite material in the form of        graphite-epoxy prepreg fabric on the tool's outer surface.        Segments of the fabric about 45 inches in height, each        circumferentially subtending about 60°, are placed on the outer        surface of the tool, adjacent segments overlapping one another        by about 1 inch. No tape or adhesives are used to secure        overlapping fabric segments since they may contaminate the final        composite structure. About 3 or 4 such plies are layered on at a        time;    -   (2) Applying two-sided vacuum bag sealant tape around the top        and bottom peripheries of the outer surface of the tool and        along the splice plate areas on the inner surface of the tool to        form the sealant bead. The two-sided tape is applied to the        outer surface of the tool, and not to the surface of the        composite material. On the outer surface of the tool, a gap of        about 5 to 7 inches is left between the circumferentially        extending upper and lower edges of the composite material and        the circumferentially extending upper and lower sealant beads;    -   (3) Applying polymer film to form a first vacuum bag around the        fabric and along the splice plate areas. A first portion of        polymer film is wrapped around the circumference of the tool        such that it contacts and seals against the upper lower beads of        sealant tape in the manner described above. Additionally, each        of four second portions of polymer film is applied in sealing        arrangement against a corresponding one of the four tape beads        that extend around each splice plate, in the manner described        above. The first portion of polymer film sealingly engages the        four second portions of polymer film at each notch pair;    -   (4) Compacting the plies against the tool surface by applying a        vacuum to the first vacuum bag. A metal fitting is installed on        the vacuum bag, such as by taping with sealant tape, a first end        of a hose is connected to the fitting and a second end of the        hose is connected to a vacuum pump. The suction exerted by the        vacuum pump is sufficient to compact the composite material.        Therefore, no mechanical pressure other than that provided by        the plastic film of the vacuum bag pressing against the        composite material is needed to perform the compaction; and    -   (5) After compacting for 20-30 minutes, releasing the vacuum and        removing the first vacuum bag and sealant tape. At this point,        the composite materials have been compacted.

Next, in a pre-curing phase 508, the tool with the compacted fabricthereon is prepared for the autoclave. Preparation for curing entails:

-   -   (1) Installing thermocouples on the tool and on the composite        material to monitor the curing process;    -   (2) Applying breather cloth over the compacted composite        material. In a preferred embodiment, the breather cloth is a        nylon mat, such as Model No. Ultraweave 1332, available from        Airtech International of Huntington Beach, Calif.;    -   (3) Applying a fresh layer of two-sided vacuum bag sealant tape        and polymer film to form a second vacuum bag in the same manner        as described above with respect to the first vacuum sealant bag.        The second vacuum bag is formed over the breather cloth which        itself covers the compacted composite material; and    -   (4) Applying vacuum to the second vacuum bag and performing a        leak test by applying a vacuum and gauging the pressure to        determine whether a leak is present.

After this, the tool, with the composite materials applied thereon,along with the breather cloth, is cured in an autoclave. The autoclavecuring phase 510 entails:

-   -   (1) Moving the tool 100 into the autoclave and hooking up vacuum        and thermocouple connections;    -   (2) Closing the autoclave door and running through a        predetermined heat and pressure cycle to cure the composite. The        vacuum bag remains under vacuum until the autoclave pressure is        high enough above atmospheric pressure, at which point the        vacuum bag is vented to atmospheric pressure. The bag is        monitored to ensure that it does not go to positive pressure        during the cure cycle, positive pressure indicating a leak; and    -   (3) Opening the autoclave and removing the tool 100 with the        tubular composite formed thereon.

After curing in the autoclave, the composite inner skin is removed fromthe tool 100. The composite inner skin removal process 512 entails:

-   -   (1) Removing the vacuum bag and the breather cloth;    -   (2) Removing bolts securing the top ring 170 to the sectors and        then removing the top ring;    -   (3) Removing bolts securing the splice plates 402 to the        flanges;    -   (4) Removing the splice plates 402 from between adjacent pairs        of sectors;    -   (5) Installing the hand wheels 224, 226, 228 and shafts 348;    -   (6) Hooking up pressurized air to a selected one of the smaller        movable sectors 186, 188 to create an air bearing;    -   (7) Removing the pins and bolts securing the selected movable        sector 186, 188 to the base 190;    -   (8) Slowly sliding the selected movable sector (with the        assistance of the air bearing) and progressively releasing the        composite skin from the tool surface while supporting the bottom        and/or top edges of the skin to prevent it from falling;    -   (9) Repeating steps (6), (7) and (8) for the other smaller        movable sector 188, 186 and then the larger movable sector 184;        and    -   (10) Lifting the composite inner skin of the tool from the tool        100.

It is understood that there may be other steps in each of theabove-described phases. It is also understood that the some of the stepsin one or more of the above-described phases may be taken out of thesequence presented above.

Once the composite inner skin is formed, it generally is subject toadditional processing, such as perforation for acoustic attenuation.This, however, is done by a separate process using separate tools. Theacoustic core and the outer skin are also formed using separateprocesses and separate tools.

An acoustic inner barrel may be formed by bonding together the compositeinner skin, the acoustic core and the outer skin, with help of the tool100. FIG. 13 shows a process 600 to accomplish this. First, in step 602,the composite inner skin is placed over a slightly collapsed tool 100and the tool is then adjusted to the molding position such that theouter surface of the tool supports the inner skin. As indicated bypreliminary step 599, the composite inner skin may first have beenmolded on the tool, the sectors retracted and the composite inner skinremoved from the tool, and only then subsequently repositioned on thetool. Next, in step 604, the acoustic core (e.g., honeycomb coretypically used in engine nacelles) is positioned over the compositeinner skin and bonded thereto. After this, in step 606, the outer skinis positioned over the acoustic core and bonded thereto. Finally, instep 608, the bonded inner skin/core/outer skin assembly is removed fromthe tool. People skilled in the art understand how to bond adjacentlayers for such an acoustic liner.

In the foregoing discussion, the tool 100 was suitable for making acomposite tubular structure. It is understood, however, that certainfeatures disclosed herein may also be used in conjunction with tools formaking composite non-tubular structures. Thus, features such as the airbearings, the splice plates, the notches, the removable hand wheel andshaft, and the vacuum bags, among others, may find use in other toolsettings where two sectors, at least one of which is movable relative tothe other, has a joint formed therebetween.

While the present invention has been described herein above inconnection with a plurality of aspects and embodiments, it is understoodthat these aspects and embodiments were presented by way of example withno intention of limiting the invention. Accordingly, the presentinvention should not be limited to any specific embodiment or aspect,but rather construed in breadth and broad scope in accordance with therecitation of the claims appended hereto.

1. A tool for making a composite tubular structure, the tool beingadjustable between a molding position and a non-molding position, thetool comprising: a base; and a plurality of sectors mounted on the base,the plurality of sectors including at least one fixed sector that isfixed relative to the base and at least two movable sectors, each of themovable sectors being movable in a radial direction and separable fromall the other sectors.
 2. The tool according to claim 1, furthercomprising splice plates positioned between adjacent sectors, when thetool is in the molding position.
 3. The tool according to claim 2,wherein the splice plates have a T-shaped cross-section.
 4. The toolaccording to claim 2, wherein the splice plates maintain alignment ofadjacent sectors.
 5. The tool according to claim 2, wherein outersurfaces of the splice plates form a portion of an outer contour of thetool and maintain a maximum step difference along edges of adjacentsectors that is less than 0.05 inches.
 6. The tool according to claim 1,wherein each of the movable sectors rests on at least one air bearing tofacilitate movement in said radial direction.
 7. The tool according toclaim 6, wherein the at least one air bearing comprises a flat portionof a movable sector.
 8. The tool according to claim 6, furthercomprising a nozzle attached to said movable sector and connectable to acompressed air source to thereby supply air to said at least one airbearing.
 9. The tool according to claim 1, further comprising at leastone removable hand wheel operatively connected to a correspondingremovable shaft, wherein turning the hand wheel moves a correspondingsector in the radial direction.
 10. The tool according to claim 9,wherein the at least one removable hand wheel and the removable shaftare mounted on separate hinged blocks.
 11. The tool according to claim10, wherein the sectors and the hinged blocks are made from a samematerial.
 12. The tool according to claim 1, comprising a pair ofcutouts formed in the upper facing corners of adjacent sectors, thecutouts cooperating to form a notch, when the tool is in the moldingposition.
 13. The tool according to claim 1, comprising a total of foursectors, one fixed sector and three movable sectors.
 14. A method formolding a tubular composite inner skin for an acoustic inner barrel, themethod comprising: providing a tool that is adjustable between a moldingposition and a non-molding position, the tool comprising: a base; and aplurality of sectors mounted on the base, the plurality of sectorsincluding at least one fixed sector that is fixed relative to the baseand at least two movable sectors, each of the movable sectors beingmovable in a radial direction and separable from all the other sectors;adjusting the movable sectors until the tool is in the molding position;applying composite material on an outer surface of each sector; curingthe composite material to form an inner skin; and removing the innerskin from the outer surface.
 15. The method according to claim 14,further comprising: turning at least one hand wheel mounted on the toolto adjust the movable sectors; and removing the at least one hand wheelfrom the tool, prior to curing the composite material.
 16. The methodaccording to claim 14, further comprising: moving the tool into anautoclave with the composite material still on the outer surface, priorto curing the composite material.
 17. The method according to claim 14,further comprising, prior to curing: placing sealant proximate upper andlower edges of outer panels of the sectors, said sealant extendingacross notches formed between adjacent sectors; and placing a firstportion of film over the composite material, said first portion of filmcontacting said sealant.
 18. The method according to claim 17, furthercomprising, prior to curing: placing sealant on an inner surface thetool, said sealant surrounding a splice plate joining two adjacentsectors; and placing a second portion of film over said splice plate,said second portion of film contacting said sealant.
 19. The methodaccording to claim 18, further comprising, prior to curing: placingsealant proximate upper and lower edges of outer panels of the sectors,said sealant extending across notches formed between adjacent sectors;and placing a first portion of film over the composite material, saidfirst portion of film contacting said sealant; and sealingly joiningtogether end sections of the first and second portions of film in saidnotches.
 20. The method according to claim 14, further comprising, priorto curing: placing a first portion of film over the composite material;and placing at least one second portion of film over a portion of aninner surface of the tool such that the at least one second portion offilm covers a splice plate joining two adjacent sectors.
 21. The methodaccording to claim 20, further comprising sealingly joining together endsections of the first and second portions of film in notches formedbetween adjacent sectors.
 22. A tool for making a composite tubularstructure, the tool being adjustable between a molding position and anon-molding position, the tool comprising: a base; a plurality ofsectors mounted on the base, the plurality of sectors including at leastone fixed sector that is fixed relative to the base and at least twomovable sectors; each of the movable sectors being movable in a radialdirection and separable from all the other sectors; each of the movablesectors resting on at least one air bearing to facilitate movement alongan upper surface of said base; and each of the movable sectors beingoperatively connected to a removable hand wheel operatively connected toa corresponding removable shaft, wherein turning the hand wheel moves acorresponding sector; and a plurality of splice plates, with one spliceplate positioned between adjacent sectors, when the tool is in themolding position.
 23. A tool for making a composite tubular structure,the tool being adjustable between a molding position and a non-moldingposition, the tool comprising: a base; a plurality of sectors mounted onthe base, the plurality of sectors including at least one fixed sectorthat is fixed relative to the base and at least two movable sectors; anda plurality of splice plates, with one splice plate positioned betweenadjacent sectors, when the tool is in the molding position.
 24. A toolfor making a composite tubular structure, the tool being adjustablebetween a molding position and a non-molding position, the toolcomprising: abase; and a plurality of sectors mounted on the base, theplurality of sectors including at least one fixed sector that is fixedrelative to the base and at least two movable sectors; wherein each ofthe movable sectors rests on at least one air bearing to facilitatemovement along an upper surface of said base.
 25. A tool for making acomposite tubular structure, the tool being adjustable between a moldingposition and a non-molding position, the tool comprising: a base; and aplurality of sectors mounted on the base, the plurality of sectorsincluding at least one fixed sector that is fixed relative to the baseand at least two movable sectors; and each movable sector beingoperatively connected to a removable hand wheel operatively connected toa corresponding removable shaft, wherein turning the hand wheel moves acorresponding sector.
 26. The tool according to claim 25, wherein eachremovable hand wheel and its corresponding shaft are each mounted onseparate hinged blocks.
 27. A method for making an acoustic innerbarrel, the method comprising: providing a tool that is adjustablebetween a molding position and a non-molding position, the toolcomprising: a base; and a plurality of sectors mounted on the base, theplurality of sectors including at least one fixed sector that is fixedrelative to the base and at least two movable sectors, each of themovable sectors being movable in a radial direction and separable fromall the other sectors; placing a tubular composite inner skin over thetool while at least one of said movable sectors of the tool is in aretracted position; positioning an acoustic core over the inner skin andbonding the acoustic core thereto; positioning an outer skin over theacoustic core and bonding the outer skin thereto; and removing thebonded inner skin/core/outer skin composite structure from the tool. 28.The method according to claim 27, comprising, prior to positioning saidacoustic core over the inner skin: molding the inner skin on the tool;removing the inner skin from the tool; and subsequently re-positioningthe inner skin on the tool.
 29. The method according to claim 27,comprising adjusting the tool into the molding position after placingthe inner skin over the tool.
 30. The method according to claim 29,wherein the tool is adjusted into the molding position prior topositioning said acoustic core over the inner skin.